1. Field of the Invention
The present invention relates to a microfluidic dielectrophoresis system, in particular for the accumulation and/or concentration of dielectric, polarizable particles from a liquid medium, the use thereof, and a method for performing a dielectrophoresis, in particular for the accumulation and/or concentration of polarizable particles from a liquid medium, in particular using a microfluidic dielectrophoresis system.
2. Description of Related Art
An important area of application of dielectrophoresis is the concentration and separation of polarizable particles from a suspension. The particles may be manipulated in a fluidic channel, which is equipped with electrodes, as a flow cell. An inhomogeneous electrical field is produced by the electrodes during the dielectrophoresis by applying an AC voltage. A dipole moment, which interacts with the applied field, is induced by the inhomogeneous electrical field in the polarizable particles. The particles move either into areas of higher (positive DEP) or lower (negative DEP) field strength gradients due to a dielectrophoretic force field and may be accumulated therein in a “field cage” if necessary. Inter alia, a method has been established for the concentration of particles in which the polarizable particles are held back by positive dielectrophoresis (pDEP), while new sample volume is continuously conducted through the flow cell. After the electrode voltage, and therefore the dielectrophoretic force, is turned off, the particles may be flushed out in collected form. Because of the short range of the electrical field, microfluidic systems suggest themselves in particular for implementing the described functional principle. A typical construction of such a microfluidic system includes a microfluidic chip, which is equipped with a dielectrophoretically active channel part, which is equipped with electrodes, as a flow cell and with supply line channels. Such constructions are described, for example, in the technical publications “Strategies for dielectrophoretic separation in laboratory-on-a-chip systems” (Hughes, M. P. Electrophoresis 2002, 23, 2569) and “High-Throughput Positive-Dielectrophoretic Bioparticle Microconcentrator” (Gadish, N.; Voldman, J. Anal. Chem. 2006, 78, 7870) and the literature cited therein. A microfluidic channel system may be contacted with further components via flexible tubing. The sample volumes may be supplied from a reservoir using injector pumps or peristaltic pumps. Liquid which is no longer required may be conducted into a waste reservoir.
Such dielectrophoresis (DEP) chips, which may allow the selective separation and concentration of polarizable particles, for example, polymer particles or bioparticles, such as viruses, bacteria, or cells, possibly from complex substance mixtures, for example, for a subsequent analysis, are currently of interest in research and development. With respect to biotechnological applications, the problem often exists that bacteria, viruses, or cells must be extracted from a comparatively large sample volume. In order to conduct large liquid quantities (milliliters) through a microfluidic system in an acceptable time, comparatively large channel cross-sections and therefore large channel volumes are required. As a result, not all particles are reached by the dielectrophoretic force field and the liquid quantity required for the final flushing of the particles out of the particular channel is in turn relatively large, which limits the achievable particle concentration, and reduces the efficiency of the concentration in relation to a channel having smaller volume.
A device for the sequencing of polynucleotides is proposed in published international patent application document WO 97/07245, in which the samples may be fed using a distributor unit into separation channels which are operated in parallel and may be processed simultaneously therein, for example, separated.